1. Field of the Invention
The present invention relates to an apparatus for analyzing performance of an ATM switch, a method thereof, and an ATM switching system employing the same, and, more particularly, to an apparatus for analyzing the performance of an ATM switch with respect to a data transmission capacity for transmitting data input to the ATM switch, a method thereof, and an ATM switching system employing the same. The present application is based on Korean Patent Application No. 2001-5724 filed Feb. 6, 2001, which is incorporated herein by reference.
2. Description of the Related Art
Generally, there are synchronous communications and asynchronous communications in the communication method.
An asynchronous transfer mode (ATM) is one of the asynchronous communications that has higher data transmission efficiency when compared with time division multiplexing (TDM) of the synchronous communication methods. In the TDM method, a predetermined slot is assigned to each subscriber terminal, and thus data is transmitted only in the assigned slot. Accordingly, in the TDM method, data transmission efficiency is deteriorated, since there is a period of time when the subscriber terminal does not transmit data in the assigned slot, leaving the slot unused for the data transmission.
Compared to the TDM method, the ATM method has a higher data transmission efficiency since the ATM method makes a connection to transmit the data as necessary.
In such an ATM method, the data transmission path is determined in advance of making connection by using the connection-oriented method.
In the ATM network built by the ATM method, a cell of 53 bytes, which is a data transmission unit, is switched.
As exemplarily shown in FIG. 1, the ATM network has ATM switches for switching the cells, and also has terminals.
The ATM switches 30 are connected through a communication network, and switch the cells to the transmission path. The terminals may include computers 10, routers 20, and LAN switches (not shown), etc.
The communication services provided by the ATM network are constant bit rate (CBR) service, and an available bit rate (ABR) service. The CBR service is assigned for the connection at a constant transmission rate, while the ABR service uses a remainder transmission rate that is left after the transmission rate is assigned for connection in the CBR service.
In the ATM network, the data for the respective connections is contained in the cells (packets) and transferred through the ATM switches 30 located at the desired destination. As shown in FIG. 2, the CBR an ABR connection cells 32 are stored in buffers 31 via input ports of the ATM switches 30, and switched to output ports selected to be transferred to desired destinations. The number of CBR and ABR connections is varied dynamically according to the time.
FIG. 3 illustrates the number of connections of respective types input to the ATM switches 30 being varied according to the time. The area bounded by a dotted line, which is not hatched, represents an area where a number of CBR connections NCBR(t) are located according to the time (t). For a better understanding, specific values are given in the drawing to represent the number of CBR connections. The hatched area, which is not occupied by the NCBR(t), represents the area where a number of ABR connections NABR(t) can be located according to the time (t). A reference character ‘r’ represents a minimum number of connections for ensuring the ABR connections with respect to the processing capacity of the ATM switches 30, i.e., available transmission rates. ‘C’ represents a maximum number of connections for ensuring the CBR connections.
With a given processing capacity (transmission rate) of the ATM switches, since there is no way to obtain connection denial possibilities of CBR connections, or an average time for data transmission of the ABR connection, there is a difficulty in designing an optimum switch when building a network.